Step 10: Check In With Developers
If you’ve installed custom software on your Nexus 5, Nexus 6, Nexus 7, or Nexus 9 and you’re unsure about how to proceed with Android Marshmallow, you’ll want to get in touch with the developers and the Android community before installing.
A lot of the initial Android update problems we see come from people who are trying to sideload the software and those who are coming from a customized version of Android.
If you aren’t running stock and you are thinking about sideloading or installing Android 6.0 Marshmallow on your Nexus phone or tablet, keep an eye on your community. XDA-Developers is a great resource to dig into before you install.